1. Field of the Invention
The present invention is in the field of windmills and wind operated devices generally. More specifically, it concerns rotating cylindrical structures as contrasted with rotating planar structures, such as conventional windmills.
2. Description of the Prior Art
In the prior art some work has been done on the use of curved blades or curved winged rotors, which are adapted to rotate about a vertical axis disposed at the point where the curved wings are joined together. The S-shaped vanes or wings are the most common form of prior art. However, these have a serious disadvantage in that wind blowing into the concave portion creates a positive pressure, while negative pressure is simultaneously generated in the opposite one, restraining rotation of the rotor.
The prior art teaches that this disadvantage may be overcome by providing the S-shaped vanes or wings with louvers arranged to open and close automatically as the rotor turns, depending upon whether the surface presented to the wind is concave or convex. However, this solution of the problem has not proved to be entirely satisfactory because as the rotor picks up speed the centrifical force generated creates a tendency on the part of the louvers to function unsatisfactorily.